Interleukin-1 (IL-1) inhibits the growth of human melanoma A375-C6 cells, in vitro. The present study involves the identification of genes that are induced by IL-1 in A375-C6 cells, and from this set of genes to further characterize the genes that ore specifically associated with growth inhibition. To accomplish these objectives, poly A+ RNA was made from unexposed and IL-1 plus cycloheximide treated A375-C6 cells, and used to prepare two double-stranded cDNA libraries in vector,pcDNAII. A cDNA library enriched for IL-1 induced genes was prepared by subtractive hybridization. Differential screening of the subtraction library lead to the identification of 14 presumptive IL-1 induced genes. Two of these have been characterized by Northern hybridization and sequencing. One gene was identified as gro/MGSA and the other as c-jun. The aim of the present proposal is to study the remaining 12 presumptive IL-1 inducible genes. Genes that are induced in A375-C6 cells by IL-1 but not by serum (which is a growth factor for these cells) will be characterized as melanoma growth inhibition-specific. gro/MGSA is an example of this type of genes.Genes that are induced by IL-1 and by serum in A375-C6 cells will not be further studied. The melanoma growth inhibition-specific genes will be further characterized as tumor growth inhibition-specific as follows. IL-1 is known to cause growth inhibition in a few other tumor cell lines while in certain other tumor cells and normal cells it stimulates a proliferative response. RNA made from a number of such different cell lines that are unexposed to IL-l or exposed to IL-1 for various amounts of time will be screened with radiolabelled probes made from the melanoma growth inhibition-specific genes. Genes that are found to be induced by IL-1 in cells for which IL-1 serves as an inhibitory signal but not in cells for which IL-1 serves as a growth stimulatory signal can be expected o be specifically associated with tumor growth inhibition, and are likely to play key roles in tumor growth inhibition pathways. All inhibition-specific genes will be subjected to nucleotide sequencing so as to deduce their amino acid sequence and understand their structure, which may in turn reflect on their function in the tumor cells. A study of growth inhibition-specific genes in melanoma cells will be the first step in delineating anti-tumor pathways.